Nicolas Sarkozy's proclamation that France and Britain could together form a "greater force for good in the world" has not gone unnoticed in Berlin.

It has left critics and commentators asking whether the once cosy Paris-Berlin alliance has been pushed aside in favour of this "new brotherhood".

The German government will be closely watching future cooperation between Paris and London. But commentators have cautioned against taking the love-in too seriously and say at its heart is Sarkozy's ambitious desire to persuade the British to be more European.

"Europe needs Britain and vice versa," said today's Süddeutsche Zeitung. "But the appeal to the British to become more engaged with Europe is likely to meet with reservation in Britain." Gordon Brown, it reminded readers, "is not exactly a passionate European".

The general view from Berlin is that it will take until the end of the French presidency of the EU at the turn of the year to determine whether or not it is valid to talk of a Paris-London axis.

The inimitable Die Welt correspondent Thomas Kielinger put its most succinctly, writing: "The proof of the pudding is in the eating, as the Brits say."

The London meeting emphasised France and Britain's shared commitment tod nuclear power, a field in which Germany, with its green ideals, could find itself being increasingly isolated, the Frankfurter Allgemeine (FAZ) said.

"Berlin is not only risking its credibility with regard to its ambitious climate protection goals," the paper said, "but also its scientific and economic links to this kind of technology."

A further reason for France to pull away from Germany is its desire to develop its military strategy, for which "France is reliant on an alliance with Britain", the Berliner Zeitung said. "The old Franco-German axis is not adequate for this any more."

But it will take more than soft-soaping by Sarkozy if he wants to persuade the Eurosceptic Brown to strengthen the EU's role in future defence missions, the paper continued. "He will need more convincing than [the German chancellor, Angela] Merkel."

Ultimately, said the Hamburger Abendblatt, what the razzle-dazzle state visit was about was "two men [who] want to improve their image ... to the detriment of a woman on the continent: Merkel".

Until now, it said, Merkel's leading role in the ensemble of EU heads of state and government had been uncontested. "Sarkozy needs an ally from London to challenge her. It remains to be seen if Brown will let that happen."

The German government's response has been relaxed, pointing out that close contacts between the French and British governments are nothing new.

"Both Germany and Britain are trying to understand exactly what it is that France wants," the FAZ said. "But it is worth remembering certain constants that have grown out of the past 50 years of European history.

"One: Britain remains an island and so all attempts to anchor it at the heart of Europe have failed due to its insular mentality. Two: the heart of Europe beats within Franco-German relations." Without this, it argued, the EU would fall apart.